A substrate processing apparatus, which performs a plasma process on a semiconductor wafer (hereinafter, simply referred to as a “wafer”) serving as a substrate, includes a chamber (processing chamber) that accommodates a wafer therein and can be depressurized; a susceptor (mounting table) installed at a lower part within the chamber; and a shower head (upper electrode) provided within the chamber so as to face the susceptor. The susceptor is configured to mount the wafer thereon and serves as a mounting electrode applying a high frequency power from a connected high frequency power supply into the chamber. The shower head introduces a processing gas into the chamber. Further, the shower head is grounded to serve as a facing electrode. In this substrate processing apparatus, the processing gas supplied into the chamber is excited into plasma by the high frequency power, and the wafer is plasma-processed by the plasma.
Conventionally, in order to appropriately distribute the plasma in a space between the shower head and the susceptor, there has been developed a substrate processing apparatus having a movable susceptor, thereby adjusting a thickness (hereinafter, referred to as a “gap”) of the space between the shower head and the susceptor. Besides, on account of the restriction on the layout around the substrate processing apparatus, a substrate processing apparatus having a movable shower head, not the movable susceptor, is recently under development.
FIG. 4 is a cross sectional view schematically illustrating a configuration of a conventional substrate processing apparatus having a movable shower head.
In a substrate processing apparatus 100 of FIG. 4, a shower head 103 is installed within a cylindrical chamber 101 so as to face a susceptor 102. The shower head 103 is formed into a substantially circular plate shape having an outer diameter substantially the same as an inner diameter of the chamber 101. The shower head 103 is configured to vertically move like a piston within the chamber 101 by a non-illustrated lift mechanism. In FIG. 4, the shower head 103 at the lowermost position is indicated by a solid line, and the shower head 103 at the uppermost position is indicated by a dashed line.
The shower head 103 includes a processing gas introducing unit having a gas flow path 104, a buffer room 105, and gas holes 106; and a gas feed pipe 107 connected to a gas supply source (not shown) for supplying a processing gas into the processing gas introducing unit from the outside. Further, a bellows 112 having a hermetically sealing function is concentrically installed at an outer peripheral portion of a shaft 111 on which the shower head 103 as a vertically movable electrode is held. Since the gas supply source is typically fixed and not moved while the shower head 103 moves up and down as stated above, the gas feed pipe 107 needs to be bent depending on a vertical movement of the shower head 103.
Typically, a flexible tube is known as a pipe for feeding a fluid toward a movable component from a fixed fluid supply source. For example, the flexible tube has been used as a pliable heat insulating pipe for feeding liquefied nitrogen toward a movable door shroud from a vacuum container in a space environment simulator (see, for example, Patent Document 1).
As shown in FIG. 5, however, since a flexible tube 108 includes a thin metal pipe 109 on which a plurality of waves is formed; and a metal mesh blade 110 enclosing the metal pipe 109, it has a relatively high stiffness against bending and thus is lack of flexibility. Accordingly, when the flexible tube 108 is largely bent, a great stress may be easily generated. Thus, when such a flexible tube is employed together with a movable component having a long displacement (moving distance), it may be broken in an early stage. Accordingly, it is difficult to use the flexible tube 108 as the gas feed pipe for supplying the processing gas into the shower head 103 which frequently moves up and down while having a long displacement of, e.g., about 70 mm in a vertical direction.
That is, the flexible tube is not designed to be repetitively bent, and it has a finite lifetime due to an irregular breakdown. Accordingly, the flexible tube needs to be replaced in a cycle of about one year, thus raising a safety issue related to the lifetime. Further, an integrally formed bellows not designed to be bent repetitively raises the same problem as that of the flexible tube. Thus, it is difficult to use such a bellows as the gas feed pipe for supplying the processing gas into the shower head 103 which frequently moves up and down.
Meanwhile, using a rotary joint coupler at a movable portion of the gas feed pipe may be considered. Since, however, the rotary joint has a physical sliding part, it may be difficult to avoid particle generation. Thus, its application to the substrate processing apparatus in which the particle generation largely affects a quality of a final product is deemed to be unpractical.
Further, it may be considered to use a bellows instead of the flexible tube or the rotary joint coupler. The bellows includes a metal pipe formed by coupling several circular ring-shaped members (hereinafter, referred to as “pieces”) each having a mountain-like longitudinal cross sectional shape. Thus, the bellows has a relatively low stiffness against bending and has a sufficiently high flexibility. Accordingly, even when it is applied as a displacement-absorbing member for the shower head 103 which frequently moves a long distance, it may not be broken in an early stage because no great stress is generated thereon.
Patent Document 1: Japanese Patent Laid-open Publication No. 2003-137200
However, although a bellows having a relatively low stiffness against bending and a high flexibility is used as the gas feed pipe for supplying a gas into the vertically-moving shower head, an installation space for the bellows needs to be additionally secured if the bellows is used only for the gas pipe. Accordingly, it is difficult to secure the installation space on a top surface of an upper unit of the substrate processing apparatus including many components. Thus, there arises a layout problem.
Further, since the bellows is of a higher price as compared to the flexible tube or the like, the length and the number of bellows used in the apparatus need to be minimized.